[Reprinted  from  Biological  Bulletin.  Vol.  X.,  No.  i,  December,  1905.] 


/ 


THE  PROGRESSIVE  ODOR  OF  ANTS. 


ADELE  M.  FIELDE. 


I.  Statement  of  Hypotheses  Based  on  Recent  and 
Former  Experiments. 

I.  The  Specific  Odor. — The  mother-ant  transmits  to  her  off- 
spring the  distinctive  odor  which  is  identical  for  ants  of  all  ages 


and  of  both  sexes  within  the  species.  This  odor  is  appreciated 


among  ants  by  organs  near  the  proximal  end  of  the  funicle.1 

2.  Progressive  Odor.  — Female  ants,  including  queens  and 
workers,  have,  besides  their  specific  odor,  an  odor  which  may  be 
termed  progressive.  Queens  of  different  lineage  have  different 
progressive  odors.  In  a queen  this  odor  is  either  unchanging  or 
changes  very  slowly,  and  it  is  similar  to  that  of  her  newly- 
hatched  female  offspring. 

a.  As  worker-ants  advance  in  age  their  progressive  odor 
intensifies  or  changes  to  such  a degree  that  they  may  be  said  to 
attain  a new  odor  every  two  or  three  months.  This  progressive 
odor  is  appreciated  among  ants  by  organs  in  the  penultimate 
joint  of  the  funicle.2 

b.  Male  ants  have  no  progressive  odor  unless  it  be  super- 
ficially incurred  through  association  with  workers  ; but  the  male 
carries  latent  in  his  spermatozoa  the  progressive  odor  of  his 
mother.  In  other  words  the  progressive  odor  is  always  recessive 
in  the  male  ant. 

c.  The  progressive  odor  of  each  new  generation  of  females  is 

1 “Artificial  Mixed  Nests  of  Ants,”  A.  M.  Fielde,  Biological  Bulletin',  Vol. 
V.,  No.  6,  November,  1903,  p.  320. 

2 “ Farther  Study  of  an  Ant,”  A.  M.  Fielde,  Proceedings  of  the  Academy  of 
Natural  Sciences , November,  1901,  p.  531. 


2 


ADELE  M.  FIELDE. 


determined  by  the  odor  of  the  mother  latent  in  her  egg,  and  the 
odor  of  the  father’s  mother  latent  in  the  spermatozoon.  The 
progressive  odor  therefore  changes  in  each  generation  of  females. 

d.  The  progressive  odor  manifest  in  female  ants  is  the  cause  of 
the  separation  of  ants  of  the  same  species  into  hostile  colonies, 
and  is  of  great  advantage  to  the  ants  in  their  individual  and  their 
communal  life. 

3.  The  Incurred  Odor.  — An  ant  may  incur  from  its  associates 
an  odor  which  is  not  inherent  in  itself,  and  which  may  be 
removed  by  washing.  It  may  be  transferred  from  ant  to  ant 
through  air  or  through  water.  It  arises  from  the  substances 
that  give  the  specific  odor  and  the  progressive  odor  and  that 
create  the  nest-aura. 

II.  Recent  Experiments  with  the  Progeny  of1  a Single 
Queen,  Componotus  Pennsylvanicus. 

In  1901  I found  that  the  odor  of  working-ants  of  Stenamma 
fulvuni  piceum  changes  with  their  age,1  forty  days  being  the  mini- 
mum of  time  in  which  there  occurs  a change  so  great  as  to  effect 
the  behavior  of  ants  of  the -same  colony  toward  one  another  at 
their  first  meeting. 

In  1902  my  further  experiments  indicated  that  a cause2  for  the 
hostility  of  one  colony  toward  another  of  the  same  species  and 
variety  is  a difference  in  odor  coincident  with  difference  in  the  age 
of  the  colonies. 

In  1904  my  observations  on  several  species  of  ants,3  represent- 
ing three  subfamilies,  gave  further  evidence  of  their  change  of 
odor  with  advance  of  age,  and  indicated  that  the  odor  of  the  queen 
is  unchanging,  or  that  her  odor  changes  much  more  slowly  than 
does  that  of  the  workers. 

I have  now  had  under  observation  for  more  than  two  years  a 
colony  of  Camponotus  pennsylvanicus , in  which  the  assertion  of  a 

1 “ A Study  of  an  Ant,”  Proceedings  of  the  Academy'  of  Natural  Sciences  of 
Philadelphia , July,  1901,  p.  449. 

2 “ Notes  on  an  Ant,”  Proceedings  of  the  Academy  of  Natural  Sciences  of  Phila- 
delphia^ September,  1902,  p.  609  ; “ Cause  of  Feud  Between  Ants  of  the  Same 
Species,”  Biological  Bulletin,  Vol.  V.,  No.  6,  November,  1903,  p.  328. 

3“  Power  of  Recognition  Among  Ants,”  Biological  Bulletin,  Vol.  VII.,  No. 
5,  October,  1904,  p.  244. 


THE  PROGRESSIVE  ODOR  OF  ANTS. 


3 


progressive  odor  in  the  workers  is  definite  and  indisputable,  the 
five  successive  broods  included  in  the  experiment  being  the  issue 
of  one  queen. 

The  N Queen.  — This  queen  was  captured  on  Nonamesset 
Island,  July  28,  1903.  She  was  then  dealated  and  was  probably 
the  mother  of  the  hundred  workers  seen  in  her  wild  nest,  and 
also  of  the  ants  that  afterwards  hatched  from  the  many  cocoons 
brought  with  her  to  the  laboratory.  She  remained  under  my 
care  and,  unless  another  is  indicated,  she  is  the  queen  referred  to 
in  the  herein  recorded  experiments. 

The  N 1 Group  of  Workers. — Some  of  the  captured  workers 
were  transferred  to  Dr.  Irving  A.  Field,  and  they  remained  segre- 
gated in  his  care,  usually  at  Harvard  University,  until  the  time 
of  the  experiment  in  which  they  appear.  As  no  other  than  male 
offspring  had  appeared  in  this  group  during  the  two  years  of  its 
separation  from  the  queen  mother,  the  workers  composing  it  in 
August,  1905,  were  certainly  acquainted  with  the  queen  pre- 
vious to  her  capture  in  July,  1903.  Of  the  age  of  these  workers 
of  course  nothing  more  was  known  than  that  it  exceeded  two 
years. 

On  August  6,  1905,  I introduced  into  this  nest,1  where  there 
were  six  major  and  five  minor  workers  and  about  thirty  larvae 
from  their  own  eggs,  the  queen-mother  from  whom  these  eleven 
workers  had  been  separated  for  two  years.  The  queen  showed 
instant  hostility,  seized  a major  worker  by  one  of  its  mandibles, 
braced  herself  on  the  sponge  and  held  her  prisoner  there  during 
the  ensuing  seven  hours.  All  the  other  workers,  sometimes  six 
at  a time,  examined  the  queen  meanwhile.  They  patted  her  with 
their  antennae,  nabbed  her  gently,  and  licked  her  back  and  legs. 
Two  of  them,  touching  her  body  with  their  antennae,  appeared  to 
dance  for  joy,  shuffling  their  feet  with  great  rapidity  during 
several  consecutive  minutes.  The  queen  then  began  to  drag  the 
worker  that  she  had  seized,  and  upon  my  releasing  the  latter,  took 
a position  near  the  larvae-pile,  as  if  to  claim  her  incipient  grand- 
sons as  her  exclusive  property,  opening  her  mandibles  at  every 
worker  who  approached.  Then  followed  a most  curious  and  pro- 

1 All  the  artificial  nests  referred  to  in  this  paper  were  of  the  Fielde  pattern.  See 
“Portable  Ant-Nests,”  Biological  Bulletin,  Vol.  VII.,  No.  4,  September,  1904. 


4 


ADELE  M.  FIELDE. 


longed  effort  on  the  part  of  the  workers  to  placate  the  queen- 
mother.  They  surrounded  her  at  all  times,  offering  her  regurgi- 
tated food.  Whichever  way  she  turned,  there  stood  a humble 
servant  with  a proffered  mouthful  of  pabulum.  As  many  as 
seven  workers  simultaneously  offered  nourishment  to  her.  Every 
worker  of  the  eleven  seemed  bent  upon  wooing  and  winning  her, 
and  she  was  not  for  a moment  left  without  attention.  These 
efforts  were  unceasingly  continued,  and  were  meeting  with  a fair 
degree  of  success,  when  I removed  the  queen  on  the  following 
morning. 

This  experiment  showed  that  the  workers  all  recognized  the 
odor  of  their  queen  after  two  years  of  separation  from  it,  and  that 
the  segregated  workers  had  during  the  same  interval  acquired  an 
odor  unfamiliar  to  the  queen,  who  had  meanwhile  met  none  of 
her  daughters  who  were  over  fifteen  months  old.  It  also  showed 
that  major  workers,  having  in  this  species  nearly  the  same  form 
and  sometimes  nearly  the  same  bulk  as  has  the  queen,  are  like 
minor  workers  in  having  a progressive  odor. 

On  August  7 I introduced  into  this  Ni  group  a marked  major 
and  a marked  minor  worker,  daughters  of  the  N queen,  but 
many  months  younger  than  any  of  the  ants  in  this  group.  The 
visitors  were  received  with  signs  of  curiosity,  but  with  perfect 
amiability,  though  no  younger  sisters  had  been  encountered 
within  two  years  by  these  Ni  ants.  The  odor  of  the  younger 
sisters  was  perfectly  recognized  by  the  eleven  residents,  and  I 
removed  the  former. 

I then  introduced  a young  winged  queen  of  the  same  species, 
Camponotus  pennsylvanicus,  but  of  an  alien  colony.  The  resident 
ants  attacked  her  instantly  and  with  exceeding  virulence.  In  an 
instant  she  lost  an  antenna,  one  worker  was  pulling  out  her 
remaining  antenna,  and  three  others  were  dragging  her  by  her 
legs.  The  scrimmage  was  fierce,  and  before  I removed  the  in- 
truder four  of  the  residents  had  received  injuries  that  resulted 
in  their  deaths.  The  residents  had  given  to  the  alien  queen 
a reception  strongly  contrasted  with  that  accorded  to  their  own 
queen-mother  ; while  the  havoc  wrought  by  the  alien  queen 
indicated  that,  if  unable  to  escape  from  the  nest,  she  might  have 
destroyed  all  the  workers  and  have  remained  a fostering  mother 
to  their  larvae. 


THE  PROGRESSIVE  ODOR  OF  ANTS. 


5 


The  N2  group.  — During  the  first  week  in  August,  1903,  the 
queen  deposited  about  a hundred  eggs,  and  from  these  were 
reared  five  minor  workers,  denoted  here  as  the  N2  ants.  These 
workers  hatched  between  April  24  and  May  10,  1904,  and  were 
therefore  some  fifteen  months  old  at  the  time  of  the  experiment 
here  recorded.  These  workers  had  never  met  other  ants  than 
those  of  their  own  segregated  group,  and  were  therefore  unac- 
quainted with  the  odor  of  ants  in  any  wise  unlike  themselves. 
They  had  never  lived  with  the  queen,  had  laid  no  eggs,  and  had 
the  care  of  no  young.  On  July  16,  1905,  I put  these  ants  into 
a new  and  very  small  nest  where  I had  isolated  the  queen-mother 
without  young.  The  five  workers  were  wholly  at  ease  with  the 
queen,  and  hastened  to  evince  their  devotion  in  ant  fashion;  but 
the  queen  opened  her  jaws  whenever  they  approached  her,  and 
was  somewhat  querulous  in  her  behavior  during  the  ensuing  two 
days.  The  queen  had  lived  during  the  previous  five  months  with 
daughters,  all  minor  ants,  less  than  five  months  old,  and  her  be- 
havior indicated  a difference  in  the  odor  of  her  younger  and  her 
older  daughters.  Her  memory  was  manifestly  less  tenacious 
than  that  of  the  workers,  who,  on  their  part  recognized  in  their 
queen  the  odor  that  had  been  their  own  in  their  infancy,  fourteen 
months  earlier. 

The  Nj  group.  — This  group  consisted  of  two  major  workers 
hatched  in  July,  1904,  and  four  of  their  younger  sisters,  minor 
workers,  over  five  months  and  less  than  a year  old,  all  the  issue 
of  the  N queen.  The  two  majors  were  acquainted  with  sisters 
older  than  themselves,  while  the  minors  knew  no  sister  older 
than  these  two  majors.  The  members  of  this  group  had  all  lived 
with  the  queen,  and  had  been  separated  from  her  and  living  in 
segregation  since  February  14,  1905.  They  had  deposited  no 
eggs,  and  they  had  the  care  of  a few  introduced  larvae.  On  July 
18,  1905,  I introduced  into  this  group  a sister  nine  months  older 
than  the  oldest  in  the  group.  The  majors,  who  had  had  acquaint- 
ance with  sisters  much  older  than  themselves,  did  not  attack  the 
newcomer  at  all,  while  every  one  of  the  minors,  never  having 
met  a sister  so  old  as  was  the  visitor,  attacked,  dragged  and 
finally  killed  her. 

It  appeared  that  the  behavior  of  the  two  major  workers  was 


6 


ADELE  M.  FIELDE. 


dictated  by  memory,  while  that  of  the  four  minor  workers  was  an 
effect  of  hostility  created  by  the  presentation  of  an  unfamiliar 
odor.  The  major  workers  were  either  wanting  in  compassion, 
or  else  they  lacked  means  of  communicating  with  their  younger 
sisters,  for  although  they  were  each  double  the  size  of  any  minor 
ant  in  the  group,  they  did  not  interfere  in  behalf  of  the  victim. 

The  N4  Group . — The  queen  was  transferred  without  eggs  or 
young  to  a new  nest  on  July  14,  1904.  She  laid  no  eggs  there- 
after until  December,  1904,  and  from  the  eggs  then  deposited  the 
five  minor  workers  constituting  the  N4  group  were  hatched 
between  February  19  and  March  23,  1905.  These  workers  were 
therefore  four  or  five  months  old  at  the  time  of  the  experiment. 
On  July  16,  1905,  I removed  the  queen  from  the  nest,  leaving  the 
five  workers  in  charge  of  twenty  larvae,  the  issue  of  the  queen’s 
December  eggs.  Into  this  group  of  five  minors,  who  had 
never  met  older  ^isters,  I introduced  one  of  the  majors  from 
group  N3,  now  just  a year  old,  and  twice  or  thrice  the  bulk 
of  any  of  the  five  residents.  The  introduced  ant  was  instantly 
and  violently  attacked  by  three  residents.  This  attack  indicates 
that  the  major,  like  the  minor  ants,  like  in  shape  and  size  as  they 
are  to  the  queen,  change  their  odor  with  advance  in  age,  as  do 
minor  workers. 

Having  removed  this  visitor,  I introduced  a marked  large 
minor  worker,  fourteen  months  older  than  the  residents,  a sister 
of  theirs,  hatched  from  eggs  deposited  by  the  queen  in  August, 
1903.  This  visitor  was  likewise  violently  attacked,  every  one  of 
the  five  residents  manifesting  hostility  to  her,  and  the  next  day  I 
found  her  mangled  body  on  their  rubbish  pile. 

The  N$  Group.  — This  group  consisted  of  two  minor  workers, 
the  issue  of  the  queen’s  December  eggs,  sequestered  in  their 
cocoons  and  hatched  on  September  8,  1905.  They  were  at 
once  placed  in  segregation  in  a new  nest,  with  a few  larvae  and 
cocoons  from  their  mother’s  eggs.  Ten  days  later  these  ants 
drove  away  from  their  pile  of  young  any  member  of  the  N4 
group  of  sisters  six  months  older  than  themselves. 

In  these  experiments  it  appears  that  it  is  the  age  of  the  work- 
ers, not  the  age  of  the  queen  at  the  time  when  she  deposits  the 
eggs  from  which  the  workers  issue,  that  determines  at  any  date 


THE  PROGRESSIVE  ODOR  OF  ANTS. 


7 


their  progressive  odor.  All  the  ants  engaged  in  this  last  men- 
tioned experiment  were  certainly  the  issue  of  the  eggs  laid  by  the 
queen  early  in  December,  1904.  That  there  is  similar  progress 
in  odor  among  ants  of  the  same  age  and  species  is  indicated  by 
an  immediate  and  amicable  association  of  ants  that  are  reunited 
after  a period  of  separation  so  long  as  two  years.1 

Whether  two  mutually  hostile  groups  could  be  created  from 
among  the  worker-progeny  of  a single  queen  would  depend  on 
power  of  memory  in  the  older  workers.  By  segregating  from 
the  pupa-stage  the  broods  of  different  summers,  it  would  be 
found  that  the  younger  sisters  would  always  be  hostile  to  the 
older  sisters,  because  the  older  sisters  would  present  an  unfamiliar 
odor  to  the  younger.  The  hostility  of  the  older  sisters  toward 
the  younger  would  be  nullified  by  their  memory  of  the  odors  by 
which  they  had  themselves  been  characterized  at  earlier  periods 
in  their  own  lives.  If  the  younger  sisters  bore  an  odor  which 
the  older  sisters,  through  the  lapse  of  many  years,  should  have 
forgotten,  then  the  hostility  would  become  mutual.  It  is  certain 
that  worker-ants  can  remember  for  years  an  odor  with  which 
they  have  once  become  familiar,  and  it  is  probable  that  they 
remember  such  odors  as  long  as  they  live. 

When  ants  of  different  groups  meet  amicably,  either  the  mem- 
bers of  these  groups  have  the  same  odor,  or  else  they  have  at 
some  time  in  their  lives  been  familiar  with  ants  bearing  the  pre- 
sented odor.  If  one  group  recognizes  a familiar  odor,  while  the 
other  group  discerns  a strange  odor,  then  those  finding  them- 
selves among  strangers  will  try  to  escape,  or  will  make  attack. 
There  is  no  love  at  first  sight  between  ants  of  different  odors. 

III.  The  Odor  and  the  Sense  of  Smell  in  Male  Ants. 

Male  ants  apparently  bear  a specific  odor,  beside  the  odor  that 
may  be  incurred  during  their  residence  with  nurses  in  the  home 
nest.  I have  introduced  males  of  different  species  into  the  nests 
of  Stenamma  fulvum , Cremastogaster  lineolata,  Myrmica  rubra , 
Formica  sanguine  a,  Formica  Schaufussi , Camponotus  pennsyl- 

1 “ A Cause  of  Feud  Between  Ants  of  the  Same  Species  Living  in  Different  Com- 
munities,” A.  M.  Fields,  Biological  Bulletin,  Vol.  V.,  No.  6,  November,  1903, 
P-  327- 


8 


ADELE  M.  FIELDE. 


vanicus , Camponotus  pictus , Camponotus  americanus , Lasius 
latipes,  and  Lasius  umbratus , and  all  these  males  have  invariably 
been  killed  within  a day  or  two.  If  hybridization  is  to  be 
effected  among  ants  it  will  be  necessary  to  cause  the  males  and 
females  to  become  acquainted  with  one  another  within  a few  hours 
after  hatching.  When  hatched  in  the  same  nest,  males  of  Sten- 
amma fulvum  pursue  queens  of  Cremastogaster  lineolata  with  the 
same  ardor  that  they  show  in  pursuing  queens  of  their  own 
species.  In  my  mixed  nests  the  failure  of  individuals  of  these 
two  genera  to  mate  was  manifestly  due  to  physical  and  not  to 
psychic  incompatibility. 

In  the  summer  of  1905  I had  material  in  my  stock  of  ants  for 
experiments  giving  evidence  that  the  male  ant  has  at  hatching 
the  specific  odor  of  his  virgin  worker-mother.  My  E mixed 
nest  consisted  of  workers  of  Camponotus  pictus , Formica  neoga- 
gates,  Formica  subsericea , and  Stenamma  fulvum , all  hatched 
during  the  last  week  of  July,  1904,  and  kept  in  the  same  nest 
until  the  first  day  of  January,  1905,  when  the  Stenammas  were 
segregated  apart.  They  remained  in  segregation  until  August 
22,  1905,  when  I put  into  their  small  nest,  where  there  were  ten 
workers  and  a few  eggs,  a fine  male  Camponotus  pictus , the 
offspring  of  a virgin  worker-mother  who  had  shared  the  nest  of 
these  Stenammas  until  she  was  five  months  old.  This  young 
male  was  received  by  the  resident  Stenammas  with  evident  pleas- 
ure. They  licked  him,  regurgitated  food  to  him,  and  rode  on  his 
back.  He  continued  to  live  happily  with  them  for  many  days. 
He  bore  a familiar  specific  odor,  although  hatched  among  segre- 
gated workers  of  his  species,  eight  months  older  than  any  that 
these  Stenammas  had  known  ; and  this  familiar  odor  made  him 
welcome.  His  fate  was  in  strong  contrast  to  that  of  some  of  his 
brothers  or  cousins  introduced  into  another  nest.  At  the  time 
of  these  experiments  I had  also  a nest,  marked  D,  of  eleven 
Stenamma  fulvum  workers,  that  had  hatched  in  a mixed  nest 
during  the  last  half  of  August,  1903,  and  had  lived  for  several 
months  with  Camponotus  pennsylvanicus , and  Formica  subsericea , 
but  had  never  met  a Camponotus  pictus.  These  eleven  Stenammas 
had  lived  in  segregation  since  July  17,  1904,  and  were  destitute 
of  young,  when  on  August  22,  1905,  I introduced  into  their  nest 


THE  PROGRESSIVE  ODOR  OF  ANTS. 


9 


a newly  hatched  Camponotus  pictns  male,  the  offspring  of  a virgin 
worker,  a brother  or  cousin  of  the  one  in  the  E nest  above 
mentioned.  These  ants  of  the  D nest  at  once  began  to  harry 
him,  and  although  he  was  eleven  millimeters  long  and  very 
sturdy,  while  none  of  the  Stenammas  were  more  than  five  milli- 
meters in  length,  they  harried  his  life  out  within  two  days.  Repe- 
titions of  this  experiment  gave  similar  results  in  every  case. 

The  eggs  from  which  these  Camponotus  pictus  males  were 
produced  were  deposited  by  their  virgin  worker-mothers  in  May, 
1905,  five  months  after  the  said  mothers  were  separated  from  the 
Stenammas  that  the  said  mothers  had  lived  with  during  the  first 
five  months  of  their  lives.  It  therefore  appears  that  the  male 
progeny  of  virgin  workers  have  not  the  progressive  odor  which 
characterized  their  mothers.  The  males  have,  however,  a specific 
odor,  an  odor  recognized  by  the  ants  through  certain  joints  of 
the  antennae,  and  this  odor  is  doubtless  the  stimulus  calling  forth 
the  exceeding  care  given  by  the  workers  to  young  males  with 
whose  specific  odor  they  are  familiar. 

On  August  26  I put  into  each  nest,  the  E and  the  D nests 
above  described,  two  males  of  Stenamma  fulvum.  These  males, 
the  first  of  their-species  ever  encountered  by  these  workers,  wery 
treated  alike  in  the  two  nests.  They  were  so  eagerly  grasped  be 
several  residents  at  once  that  it  seemed  as  if  they  must  lose  their 
lives  through  the  determined  efforts  of  the  workers  to  retain 
them.  They  were  not  left  free  for  several  hours  ; but  so  judi- 
cious were  their  virgin  captors  that  no  injury  was  done  to  the 
captives,  and  they  lived  in  health  and  honor  many  days  in  these 
nests.  In  the  E nest  the  Camponotus  pictns  male  continued  to  be 
their  associate.1  In  both  the  E and  the  D nests  newly  hatched 

1 A dealated  queen  Camoponotus  pictus  captured  alone  in  the  open  on  July  5j  was 
kept  in  isolation  till  August  15,  1905,  when  she  received  amicably  into  her  small 
artificial  nest  two  young  males  of  her  species,  the  offspring  of  virgin  worker  ants. 
She  licked  them,  regurgitated  food  to  them,  and  during  the  several  days  that  they 
remained  under  my  observation,  remained  in  close  companionship  with  them.  Later 
on  this  queen  also  received  in  amiable  fashion  the  virgin  mothers  of  these  males,  the 
worker-mothers  having  been  kept  by  me  in  segregation  during  their  whole  lives.  As 
this  queen  was  captured  near  the  spot  in  which  the  workers  had  their  origin  a year 
earlier,  these  ants  may  all  have  been  of  one  colony.  This  queen  killed  young  males 
o Formica  argentata  and  Stenamma  fulvum  introduced  into  her  nest. 


IO 


ADELE  M.  FIELDE. 


Stenamma  workers,  from  the  same  colony  as  were  these  males, 
were  immediately  killed. 

Since  the  males  avoid,  or  are  indifferent  to,  ants  of  other  spe- 
cies than  their  own,  unless  hatched  among  such  species  in  arti- 
ficial nests,  it  appears  probable  that  they  discern  the  specific  odor 
of  other  ants.  But  they  probably  lack  the  sub-nose  that  per- 
ceives the  progessive  odor  of  workers.  Male  ants  of  various 
species  placed  under  observation  in  one  of  my  artificial  nests, 
grouped  themselves  according  to  species,  but  did  not  quarrel 
with  males  of  species  unlike  their  own.  I infer  that  the  only 
inherent  odor  of  males  is  that  of  their  species  ; but  that  they  are 
the  medium  through  which  the  progressive  odor  of  their  female 
progenitors  is  transmitted  to  the  egg  that  produces  a female,  the 
progressive  odor  being  latent  in  the  males  and  reappearing  in 
their  female  descendants.  Only  the  egg  receiving  a spermato- 
zoon would  produce  a female,  and  this  female  would  be  endowed 
with  her  paternal  grandmother’s  tendencies  in  progressive  odor, 
the  progressive  odor  thus  manifesting  itself  only  in  the  female 
line  of  descent.  The  fact  that  the  worker  progeny  of  a queen, 
sequestered  from  the  pupa  stage,  will  receive  their  queen-mother 
or  the  queen-mother’s  sister  with  equal  pleasure,  indicates  simi- 
larity of  odor  in  the  product  of  the  same  queen’s  impregnated 
eggs. 

I venture  to  predict  that  there  will  be  found  in  female  ants 
secretory  glands  or  organs  that  are  wanting  or  are  rudimentary 
in  the  male,  and  that  these  organs  are  the  producers  of  the  pro- 
pressive  odor.  There  must  be  in  both  males  and  females  secre- 
tory  glands  or  organs  producing  the  specific  odor  which  is  com- 
mon to  both  sexes.  These  diverse  organs  might  be  identified 
through  the  possession  of  both  sets  by  the  female  and  of  a single 
set  in  the  male.  It  is  also  probable  that  the  male  lacks  the 
glands  that  secrete  the  scent  whereby  the  female  lays  down  her 
individual  path  from  the  nest,  and  he  may  also  lack  the  sub-nose 
which  discerns  this  path-scent.  The  male  seems  to  be  unable  to 
lay  a path,  and,  in  a change  of  domicile  by  the  colony,  he  is  car- 
ried bodily  by  the  females  to  the  new  nest.  It  is  through  his 
appreciation  of  the  specific  odor  and  his  lack  of  perception  of  the 


THE  PROGRESSIVE  ODOR  OF  ANTS. 


I 


progressive  odor  that  the  male  is  best  fitted  for  his  distinctive 
office  in  the  ant  world. 

IV.  The  Progressive  Odor  of  Queen  Ants. 

The  change  in  the  inherent,  transmissible,  progressive  odor  in 
a line  of  queens  is  probably  slow  and  cumulative,  but  that  such 
a change  occurs  is  evidenced  by  the  behavior  of  any  segregated 
group  of  Stenamma  fulvum  workers,  a species  in  which  the 
queens  generally  remain  in  the  colony  in  which  they  are  pro- 
duced. When  workers  from  such  a colony  are  segregated  from 
the  pupa-stage  upward,  it  becomes  difficult  to  find,  in  the  wild 
nest,  any  queen  that  these  segregated  workers  will  accept  as  their 
own.  In  this  species,  I have  reared  worker-offspring  from  queens 
that  were  sequestered  from  all  males  except  those  of  their  own 
colony,1  and  these  workers  willingly  associated  with  their  worker- 
cousins.  That  the  change  of  odor  is  but  slight  in  a single  gene- 
ration is  also  shown  by  the  fact  that  the  worker-daughters  of  a 
queen,  after  having  been  segregated  from  their  pupa-stage  upward, 
and  with  no  criterion  of  odor  save  that  of  their  own  bodies,  will 
affiliate  with  their  queen-mother  at  a first  meeting,  though  they 
always  examine  her  with  exceeding  care  before  rendering  com- 
plete homage. 

The  gradual  change  in  odor,  through  the  introduction  of  the 
male  element,  from  generation  to  generation,  may  be  crudely  re- 
presented by  the  use  of  letters  as  symbols  of  the  odor  of  queens 
of  the  same  species  and  variety. 

The  Roman  numerals  at  the  left  denote  successive  generations 
of  mated  queens. 

The  letter  a is  used  as  a symbol  of  the  odor  characterizing  two 
sister  queens  ; the  other  letters  as  symbols  of  the  odor  inherited 
from  the  paternal  grandmother. 


I. . 

a, 

I. 

a , 

II. 

a h, 

II. 

a -j-  /, 

III. 

a + b -f-  c, 

III. 

a — |—  l — |—  m 

IV. 

a -\-  b -\-  c -\-  d, 

IV. 

a -f-  l-j-  m 

+ «> 

V. 

a -(-  b -(-  c -J-  d -j-  e, 

• V. 

a -j- 1 -j-  m 

+ * + *1 

etc. 

etc. 

1 “ Notes  on  an  Ant,”  Proceedings  of  the  Academy  of  Natural  Sciences  of  Phila- 
delphia, December,  1902,  p.  605. 


ADELE  M.  FIELDE. 


12 


The  female  descendants  of  sister  queens  would  thus  become 
more  unlike  in  odor  with  every  generation. 

An  odor  providing  the  means  of  recognizing  a maternal  ances- 
tor, or  another  descendant  of  that  ancestor,  may  be  dominant 
through  more  than  one  generation  of  females. 

The  fact  that  worker  ants  who  have  never  met  any  queen  will 
as  joyfully  associate  with  their  queen-mother’s  sister  as  with  their 
own  mother,  indicates  that  sister-queens  have  the  same  odor  after 
mating  that  they  had  before  mating,  and  that  the  first  divergence 
in  odor  becomes  apparent  to  the  ants  only  in  the  offspring  of 
sister-queens  that  mated  with  males  capable  of  imparting  unlike 
odors  to  their  respective  progeny.  The  worker  ants,  having 
attained  the  distinctive  progressive  odor  characterizing  their 
mothers’  worker- offspring  for  the  current  year,  may  produce 
males  who  will  each  impart  to  his  progeny  the  distinctive  odor 
borne  by  all  the  female  issue  of  the  queen  with  whom  he  mates. 
Each  generation  in  the  line  of  queens  would  then  depart  farther 
from  the  odor  of  the  queen  ancestor,  and  we  should  find,  as  we 
do,  colonies  in  which  all  the  female  inhabitants  are  inimical  to  all 
the  female  inhabitants  of  another  colony.  There  would  also  be 
produced,  as  in  colonies  of  Stenamma  fulvum , where  queens  mate 
within  the  nest  and  remain  to  increase  its  population,  the  phe- 
nomenon of  callows  that,  if  segregated  from  the  pupa-stage, 
refuse  to  affiliate  with  queens  from  the  nest  in  which  were  depos- 
ited the  eggs  from  which  these  callows  issued. 

During  several  years  I have  been  interested  in  ascertaining 
whether  adult,  queenless  workers  would  willingly  accept  a queen 
who  was  indisputably  of  another  colony  of  their  own  species,  and 
among  many  experiments  I have  never  seen  such  an  acceptance. 
If  forced  into  association,  escape  of  either  party  being  made  im- 
possible, the  workers  may  after  a longer  or  shorter  interval  live 
peaceably  with  the  alien  queen,  as  they  also  may  do  with  alien 
workers.  But  such  forced  alliances  do  not  result  in  normal  pros- 
perity, even  when  a whole  year  is  allowed  for  the  cementing  of 
friendship.  So  exacting  are  the  ants  concerning  adherence  to 
their  standard  of  odor  that  they  prefer  a queenless  state  to  the 
presence  of  an  unknown  ant-odor.  Observations  made  by  me 
in  the  summer  of  1905  accord  with  my  earlier  ones.  Eleven 


THE  .PROGRESSIVE  ODOR  OF  ANTS. 


13 


workers  of  Stenamma  fulvum  piceum  had  been  inmates  of  one  of 
my  mixed  nests,  with  Camponotus  pennsylv aniens  and  Formica 
subsericea,  all  hatched  between  August  14  and  September  3, 
1903.  The  Stenammas  had  been  removed  from  the  mixed  nest, 
and  kept  in  segregation  since  June  23,  1904,  and  had  never  met 
a queen.  On  August  13,  1905,  I introduced  into  this  nest  a 
young,  winged  queen  of  the  same  variety  as  these  workers,  on  the 
twenty-fourth  day  after  I had  isolated  her  to  ensure  her  freedom 
from  incurred  odor.  The  queen  fled  from  the  group  of  workers 
and  constantly  tried  to  escape.  She  was  attacked  whenever  I 
forced  her  into  the  group  of  workers,  and  was  caught  and  killed 
by  them  on  the  ninth  day  of  her  sojourn.  A dealated  queen  intro- 
duced later,  from  the  wild  colony  to  which  these  workers  origi- 
nally belonged,  was  also  killed  by  them. 

Since  ants  possess  so  discriminating  a sense  of  smell,  and  are 
so  exacting  concerning  an  adherence  to  the  criterion  established 
for  their  nest,  and  since  even  those  ants  who  have  had  an  ex- 
tended experience  in  ant-odors,  and  who  have  been  queenless  for 
two  years,  refuse  to  affiliate  with  a queen  of  an  alien  odor  though 
of  their  own  variety,  we  may  hardly  expect  that  they  will  volun- 
tarily associate  with  queens  of  another  species.  During  the  sum- 
mer of  1905  I introduced  queens  of  other  species  into  segregated, 
queenless  groups  of  adult  Stenamma  fulvum , of  Formica  neoga- 
gates  and  of  Formica  Schaufussi , that  had  had  their  sense  of  smell 
highly  educated  by  long  association  with  workers  of  two  or  three 
different  species  of  ants,  but  in  every  case  the  introduced  queen 
was  killed  within  a few  days,  in  spite  of  her  constant  efforts  to 
keep  aloof  from  the  workers. 

In  no  species  of  ant  have  I found  workers  that  would  tolerate 
the  presence  of  any  queen  of  unfamiliar  odor,  nor  any  queen  that 
would  willingly  remain  among  workers  of  unfamiliar  odor. 
Although  all  species  of  ants  have  not  been  thus  tested  we  may 
well  assume  that  what  is  shown  to  be  a fundamental  trait  in  a few 
species  will  manifest  itself  in  all  species  of  the  tribe. 


4 


ADELE  M.  FIELDE. 


V.  Effects  of  the  Progressive  Odor  in  the  Communal 
Life  of  Ants. 

Since  the  queen  is  ordinarily  the  earliest  occupant  of  the  ant- 
nest,  and  since  her  callow  young  have  the  same  odor  as  herself, 
the  odor  of  her  earliest  nest  must  at  first  be  the  same  as  is  that 
of  the  queen.  Probably  this  odor  is  at  all  times  dominant  in  the 
permanent  nest ; but  as  the  progressive  odor  of  the  workers  is 
gradually  added  thereto,  the  nest-aura  would  be  thereby  modi- 
fied. The  change  in  the  nest-aura,  cumulative  with  the  age  of 
the  colony  and  the  increase  of  the  inmates,  would  be  so  gradual 
that  all  habitants  of  the  nest  would  at  all  times  find  it  familiar 
and  therefore  congenial.  The  greater  dominance  of  the  queen’s 
odor  in  the  earlier  nest  may  be  the  cause  of  the  persistence  with 
which  many  workers  cling  or  return  to  the  old  habitation  even 
after  the  majority  of  the  colony  has  for  sound  reason  removed  to 
a new  abode. 

It  appears  probable  also  that  diffused  ant-odor  is  in  direct  ratio 
to  bulk  of  ant-body,  and  that  a cause  of  the  common  activity  of 
workers  in  adding  the  lesser  to  the  larger  pile  of  brood,  some- 
times even  against  the  inhibitory  effects  of  light,  is  due  to  the 
more  manifest  odor  of  the  larger  pile. 

I have  at  different  times  during  several  years  observed  in  my 
artificial  nests  a most  curious  phenomenon  among  ants  that  had 
long  lived  amicably  together.  Several  or  many  workers  were 
seen  standing  around  one  ant  as  if  holding  a court  of  inquiry  con- 
cerning this  associate.  Sometimes  the  associate  is  proscribed, 
sometimes  rent  limb  from  limb.  This  extraordinary  behavior  is 
probably  due  to  the  victim  having  attained  a progressive  odor  that 
is  obnoxious  to  many  other  inmates  of  the  nest  because  unknown 
to  them.  This  might  happen  to  an  aged  ant  whose  horde  of  com- 
panions were  all  young.  It  might  also  happen  that  in  prowling 
for  food,  or  in  raids  made  on  the  nests  of  aliens,  the  worker  ants 
would  bring  in  alien  young  for  food,  and  that  this  much  licked 
and  tended  young  would  incur  the  progressive  odor  of  the  nurses. 
At  a later  period  the  introduced  ant  might  produce  a progres- 
sive odor  unlike  that  of  the  multitude  inhabiting  the  nest,  and  it 
would  therefore  be  doomed  to  destruction.  Ostracisms  or  violent 


THE  PROGRESSIVE  ODOR  OF  ANTS. 


5 


deaths,  such  as  sometimes  occur  in  nests  where  amity  has  long 
prevailed,  are  probably  to  be  explained  by  the  attainment  by  some 
of  the  inmates  of  a new  and  therefore  an  alarming  progressive 
odor. 

There  may  be  seen  among  ants  of  the  same  variety,  and  even 
in  the  same  individual,  all  degrees  of  attraction  and  repulsion 
towards  other  ants  at  a first  meeting  with  them.  Such  manifes- 
tations range  all  the  way  from  cuddling,  caressing,  cherishing  de- 
votion through  indifference  and  inattention,  distrust,  suspicion, 
animosity  and  enduring,  ferocious  enmity.  The  inciting  cause 
is  doubtless  the  progressive  odor  of  the  visitor,  and  the  prac- 
tical end  is  the  preservation  of  the  chemical  standard  of  the  nest. 

Whatever  the  action  of  the  ants,  it  is  always  more  obvious 
when  there  are  numerous  young  in  the  nests,  and  when  the  nest- 
aura  is  well  established. 

During  five  years  of  fairly  constant  study  of  ants  I have  seen 
no  evidence  that  their  antennae  are  the  organs  of  any  other  sense 
than  the  chemical  sense,  and  I am  convinced  that  any  statement 
concerning  the  behavior  of  ants  may  well  be  distrusted  if  it  ignore 
the  dominance  of  the  olfactory  sense  over  the  conduct  of  the  ant, 
the  ant’s  almost  inconceivable  minuteness  of  discrimination  in 
odors,  or  the  ant’s  marvelous  memory  of  odors  that  have  been 
encountered.  Only  when  ants  are  segregated  from  the  pupa- 
stage,  and  full  record  kept  of  every  experience  of  theirs  in  meet- 
ing other  ants,  can  the  investigator  truthfully  declare  that  ants 
behave  in  a certain  manner  in  the  presence  of  other  ants.  More- 
over, as  every  ant  acts  on  personal  experience  and  individual 
memory,  the  ants  should  be  considered  singly  as  well  as  in 
groups  and  communities,  when  a theory  of  their  behavior  is  to  be 
enunciated.  But  when  the  total  history  of  an  ant  is  known,  the 
investigator  may  accurately  predict  the  behavior  of  that  ant 
toward  other  ants.  There  is  exceeding  uniformity  of  behavior 
among  ants  having  an  identical  history. 

The  progressive  odor  of  the  worker  ants  is  manifestly  an  ad- 
vantage in  their  communal  life,  since  it  furnishes  the  means 
whereby  every  ant  can  recognize  its  home  and  its  fellow-citizens, 
avoiding  nests  and  communities  other  than  its  own.  The  uses  of 
this  odor  within  the  colony  may  also  be  numerous,  and  it  may 
determine  the  distribution  of  labor  in  the  ant  community. 


r 


3 0112  07283 


9878 


1 6 ADELE  M.  F1ELDE. 

Through  the  male  element,  it  probably  differentiates  the  odor 
of  queens  of  the  same  species,  enabling  the  workers  to  find,  to 
defend,  and  to  cherish  their  own  queen. 

It  differentiates  ants  otherwise  alike  ; determines  their  distribu- 
tion in  separate  communities  ; dictates  the  behavior  of  members 
of  one  colony  toward  those  of  another  colony,  and  in  connection 
with  an  acute  sense  of  smell  and  a powerful  memory,  is  a domi- 
nant factor  in  the  life  of  the  individual  ant  and  in  the  structure  of 
the  ant-col,ony. 


